Nocturnal sodium excretion, blood pressure dipping, and sodium sensitivity

Sleep and hypertension - up to date 2024

People spend one-third of their lives sleeping, and adequate, restful sleep is an essential component of a healthy life. Conversely, disruption of sleep has been found to cause various physical and mental health problems. Emerging research has shown that blood pressure (BP) during sleep is a stronger predictor of cardiovascular events than conventional office BP or daytime BP. Thus, management of both sleep health and nighttime BP during sleep is important for preventing cardiovascular events. However, recent studies demonstrated that nighttime BP is poorly controlled compared with office BP and daytime BP. This finding is understandable, given the challenges in monitoring BP during sleep and the multiplicity of factors related to nocturnal hypertension and BP variability. This review summarizes recent evidence and considers future perspectives for the management of sleep and hypertension.

Physical Activity and Urinary Sodium Excretion Circadian Rhythm: A Population-Based Cross-Sectional Pilot Study

Background/Objectives: Blood pressure (BP) is characterized by a circadian rhythm (Circr) with lower nighttime values, called dipping. Non-dipping is associated with higher CVD risk. The Circr of urinary sodium excretion (NaCle), peaking during the day, is linked to BP patterns. Physical activity (PA) is known to improve BP control and enhance the dipping phenomenon, but its possible effect on NaCle remains unclarified. This study aimed to investigate the correlation between PA and the Circr of NaCle and to determine if the relationship is independent of age, sex, BP values, dipping pattern, and salt intake. Methods: A pilot cross-sectional analysis was conducted using data from the Ticino Epidemiological Stiffness Study, involving 953 participants in Switzerland. Data collection included standardized questionnaires, blood samples, 24 h urine collections, and ambulatory BP monitoring. Participants were categorized into sedentary, partially active, and active. The effect of PA, NaCl intake, and dipping on the day/night NaCle ratio was assessed with multivariable linear regressions. Results: Participants' median age was 49 years, with 78% having normal BP values and 47% exhibiting a dipping pattern; 51% were classified as sedentary and 22% as partially active. The median NaCl intake was 7.9 g/day. The youngest subjects had a higher hourly NaCle ratio compared to older subjects. Higher NaCl intake correlated with increased BP, a phenomenon more pronounced in men and younger subjects. The hourly day/night NaCle ratio positively correlates with dipping; however, PA did not show a significant correlation with the NaCle ratio. Conclusions: This study indicates that while the day/night NaCle ratio correlates with the dipping pattern, PA is unrelated to the circadian rhythm of renal sodium handling. The beneficial effects of PA on BP and cardiovascular health thus appear to be mediated through mechanisms other than NaCle. These are explorative findings only but relativize the need for further investigations on the topic.

Susceptibility gene identification and risk evaluation model construction by transcriptome-wide association analysis for salt sensitivity of blood pressure

BACKGROUND

Salt sensitivity of blood pressure (SSBP) is an intermediate phenotype of hypertension and is a predictor of long-term cardiovascular events and death. However, the genetic structures of SSBP are uncertain, and it is difficult to precisely diagnose SSBP in population. So, we aimed to identify genes related to susceptibility to the SSBP, construct a risk evaluation model, and explore the potential functions of these genes.

METHODS AND RESULTS

A genome-wide association study of the systemic epidemiology of salt sensitivity (EpiSS) cohort was performed to obtain summary statistics for SSBP. Then, we conducted a transcriptome-wide association study (TWAS) of 12 tissues using FUSION software to predict the genes associated with SSBP and verified the genes with an mRNA microarray. The potential roles of the genes were explored. Risk evaluation models of SSBP were constructed based on the serial P value thresholds of polygenetic risk scores (PRSs), polygenic transcriptome risk scores (PTRSs) and their combinations of the identified genes and genetic variants from the TWAS. The TWAS revealed that 2605 genes were significantly associated with SSBP. Among these genes, 69 were differentially expressed according to the microarray analysis. The functional analysis showed that the genes identified in the TWAS were enriched in metabolic process pathways. The PRSs were correlated with PTRSs in the heart atrial appendage, adrenal gland, EBV-transformed lymphocytes, pituitary, artery coronary, artery tibial and whole blood. Multiple logistic regression models revealed that a PRS of P < 0.05 had the best predictive ability compared with other PRSs and PTRSs. The combinations of PRSs and PTRSs did not significantly increase the prediction accuracy of SSBP in the training and validation datasets.

CONCLUSIONS

Several known and novel susceptibility genes for SSBP were identified via multitissue TWAS analysis. The risk evaluation model constructed with the PRS of susceptibility genes showed better diagnostic performance than the transcript levels, which could be applied to screen for SSBP high-risk individuals.

Plant-Based Meat Analogs and Their Effects on Cardiometabolic Health: An 8-Week Randomized Controlled Trial Comparing Plant-Based Meat Analogs With Their Corresponding Animal-Based Foods

BACKGROUND

With the growing popularity of plant-based meat analogs (PBMAs), an investigation of their effects on health is warranted in an Asian population.

OBJECTIVES

This research investigated the impact of consuming an omnivorous animal-based meat diet (ABMD) compared with a PBMAs diet (PBMD) on cardiometabolic health among adults with elevated risk of diabetes in Singapore.

METHODS

In an 8-wk parallel design randomized controlled trial, participants (n = 89) were instructed to substitute habitual protein-rich foods with fixed quantities of either PBMAs (n = 44) or their corresponding animal-based meats (n = 45; 2.5 servings/d), maintaining intake of other dietary components. Low-density lipoprotein (LDL) cholesterol served as primary outcome, whereas secondary outcomes included other cardiometabolic disease-related risk factors (e.g. glucose and fructosamine), dietary data, and within a subpopulation, ambulatory blood pressure measurements (n = 40) at baseline and postintervention, as well as a 14-d continuous glucose monitor (glucose homeostasis-related outcomes; n = 37).

RESULTS

Data from 82 participants (ABMD: 42 and PBMD: 40) were examined. Using linear mixed-effects model, there were significant interaction (time × treatment) effects for dietary trans-fat (increased in ABMD), dietary fiber, sodium, and potassium (all increased in PBMD; P-interaction <0.001). There were no significant effects on the lipid-lipoprotein profile, including LDL cholesterol. Diastolic blood pressure (DBP) was lower in the PBMD group (P-interaction=0.041), although the nocturnal DBP dip markedly increased in ABMD (+3.2% mean) and was reduced in PBMD (-2.6%; P-interaction=0.017). Fructosamine (P time=0.035) and homeostatic model assessment for β-cell function were improved at week 8 (P time=0.006) in both groups. Glycemic homeostasis was better regulated in the ABMD than PBMD groups as evidenced by interstitial glucose time in range (ABMD median: 94.1% (Q1:87.2%, Q3:96.7%); PBMD: 86.5% (81.7%, 89.4%); P = 0.041). The intervention had no significant effect on the other outcomes examined.

CONCLUSIONS

An 8-wk PBMA diet did not show widespread cardiometabolic health benefits compared with a corresponding meat based diet. Nutritional quality is a key factor to be considered for next generation PBMAs. This trial was registered at https://clinicaltrials.gov/as NCT05446753.

Race differences in ambulatory blood pressure monitoring parameters

BACKGROUND

Mean systolic and diastolic blood pressure (SBP and DBP) on ambulatory blood pressure (BP) monitoring (ABPM) are higher among Black compared with White adults. With 48 to 72 BP measurements obtained over 24 h, ABPM can generate parameters other than mean BP that are associated with increased risk for cardiovascular events. There are few data on race differences in ABPM parameters other than mean BP.

METHODS

To estimate differences between White and Black participants in ABPM parameters, we used pooled data from five US-based studies in which participants completed ABPM (n = 2580). We calculated measures of SBP and DBP level, including mean, load, peak, and measures of SBP and DBP variability, including average real variability (ARV) and peak increase.

RESULTS

There were 1513 (58.6%) Black and 1067 (41.4%) White participants with mean ages of 56.1 and 49.0 years, respectively. After multivariable adjustment, asleep SBP and DBP load were 5.7% (95% CI: 3.5-7.9%) and 2.7% (95% CI: 1.1-4.3%) higher, respectively, among Black compared with White participants. Black compared with White participants also had higher awake DBP ARV (0.3 [95%CI: 0.0-0.6] mmHg) and peak increase in DBP (0.4 [95% CI: 0.0-0.8] mmHg). There was no evidence of Black:White differences in awake measures of SBP level, asleep peak SBP or DBP, awake and asleep measures of SBP variability or asleep measures of DBP variability after multivariable adjustment.

CONCLUSION

Asleep SBP load, awake DBP ARV and peak increase in awake DBP were higher in Black compared to White participants, independent of mean BP on ABPM.

Higher Nocturnal Blood Pressure and Blunted Nocturnal Dipping Are Associated With Decreased Daytime Urinary Sodium and Potassium Excretion in Patients With CKD

Introduction

Sodium homeostasis is intimately associated with blood pressure (BP) rhythm, and potassium excretion is closely associated with sodium excretion in the general population. However, the association between circadian sodium and potassium pattern excretion and nocturnal BP in patients with chronic kidney disease (CKD) is not elucidated.

Methods

We evaluated the correlation between the day-to-night ratio of urinary sodium and potassium excretion rate, nocturnal blood pressure, and nocturnal BP dipping in a CKD cohort.

Results

A total of 3152 (56.76% males, mean age 47.63 years) individuals with CKD were included in the study. Patients in quartile 1 (with the lowest ratio) exhibited a 12 mmHg or 9 mmHg higher nocturnal systolic blood pressure (SBP) and blunted SBP dipping than those in quartile 4 when urinary sodium or potassium excretion rate was divided into day-to-night ratios (both P < 0.001). In multivariate analyses, lower day-to-night ratio of urinary sodium was independently linked to higher nocturnal SBP and blunted SBP dipping (linear regression coefficient (95% confidence interval [CI]): -6.89 (-9.48 to -4.31), and -3.64 (-5.48 to -1.80), respectively; both P < 0.001). Similarly, compared with the highest quartile of day-to-night ratio of urinary potassium excretion rate, linear regression coefficient (95% CI) for the lowest quartile was -5.60 (-8.13 to -3.07) for nocturnal SBP, and -2.47 (-4.28 to -0.67) for SBP dipping (both P < 0.001). Moreover, urine flow rate and concentrates of sodium or potassium in the urine were positively associated with urinary sodium or potassium excretion during daytime (P < 0.001).

Conclusion

A higher nocturnal BP and a blunted nocturnal BP dipping were both independently linked to a lower excretion of sodium or potassium during the day in patients with CKD. Furthermore, a decreased urine flow rate and a diminished capacity to concentrate sodium or potassium in the urine appear to be the key contributors to a low day-to-night ratio of urinary sodium excretion or potassium rate.

Management of nocturnal hypertension: An expert consensus document from Chinese Hypertension League

Nocturnal hypertension is highly prevalent among Chinese and Asian populations, which is mainly attributed to high salt intake and high salt sensitivity. Nocturnal hypertension increases the risk of cardiovascular and all-cause mortality, independent of daytime blood pressure (BP). However, it can usually be detected by 24-h ambulatory BP monitoring, rather than routine office or home BP measurement, thus is often underdiagnosed in clinical practice. Currently, no specific guidance is available for the management of nocturnal hypertension in China or worldwide. Experts from the Chinese Hypertension League summarized the epidemiologic and pathophysiologic characteristics and clinical phenotype of nocturnal hypertension and provided consensus recommendations on optimal management of nocturnal hypertension, with the goal of maximally reducing the cardiovascular disease risks. In this consensus document, 24-h ABPM is recommended for screening and diagnosis of nocturnal hypertension, especially in the elderly, patients with diabetes, chronic kidney diseases, obstructive sleep apnea and other conditions prone to high nocturnal BP. Lifestyle modifications including salt intake restriction, exercise, weight loss, sleep improvement, and mental stress relief are recommended. Long-acting antihypertensive medications are preferred for nocturnal and 24-h BP control. Some newly developed agents, renal denervation, and other device-based therapy on nocturnal BP reduction are evaluated.

Non-Dipping Blood Pressure or Nocturnal Hypertension: Does One Matter More?

PURPOSE OF REVIEW

Nocturnal hypertension and non-dipping are both associated with increased cardiovascular risk; however, debate remains over which is a better prognosticator of cardiovascular outcomes. This review explores current literature on nocturnal hypertension and non-dipping to assess their relationship to cardiovascular disease and implications for clinical practice.

RECENT FINDINGS

While current data remain inconclusive, some suggest that nocturnal hypertension is a more reliable and clinically significant marker of cardiovascular risk than non-dipping status. Importantly, reducing nocturnal HTN and non-dipping through chronotherapy, specifically evening dosing of antihypertensives, has not been conclusively shown to provide long-term cardiovascular benefits. Recent data suggests that non-dipping, compared to nocturnal hypertension, may be falling out of favor as a prognostic indicator for adverse cardiovascular outcomes. However, additional information is needed to understand how aberrant nighttime blood pressure patterns modulate cardiovascular risk to guide clinical management.

Nocturnal systolic blood pressure dipping and progression of chronic kidney disease

The relationship between declining nocturnal blood pressure (BP) and adverse cardiovascular outcomes is well-recognized. However, the relationship between diurnal BP profile and the risk of chronic kidney disease (CKD) progression is unclear. Herein, we examined the association between nocturnal systolic SBP (SBP) dipping and CKD progression in 1061 participants at the Cardiovascular and Metabolic Disease Etiology Research Center-High Risk (CMERC-HI). The main exposure was diurnal systolic BP (SBP) profile and diurnal SBP difference ([nighttime SBP-daytime SBP] × 100/daytime SBP). The primary outcome was CKD progression, defined as a composite of ≥ a 50% decline in the estimated glomerular filtration rate from baseline or the initiation of kidney replacement therapy. During 4749 person-years of follow-up (median, 4.8 years), the composite outcome occurred in 380 (35.8%) participants. Compared to dippers, the hazard ratios (HRs) for the risk of adverse kidney outcomes were 1.02 (95% confidence interval [CI], 0.64-1.62), 1.30 (95% CI, 1.02-1.66), and 1.40 (95% CI, 1.03-1.90) for extreme dipper, non-dipper, and reverse dipper, respectively. In a continuous modeling, a 10% increase in diurnal SBP difference was associated with a 1.21-fold (95% CI, 1.07-1.37) higher risk of CKD progression. Thus, decreased nocturnal SBP decline was associated with adverse kidney outcomes in patients with CKD. Particularly, patients with non-dipping and reverse dipping patterns were at higher risk for CKD progression than those with a dipping pattern.

Effects of Nondipping Blood Pressure Changes: A Nephrologist Prospect

Blood pressure (BP) variations depend on various internal, environmental, and behavioral factors. BP fluctuations occur both in normotensive and hypertensive people. Although it fluctuates over the 24-hr day and night, the morning BP increases after waking up and declines throughout sleep. It is typical for BP to decrease by 10% to 20%, while sleeping, known as dipping BP. However, if there is no decrease in nighttime mean systolic BP or a drop of less than 10 mmHg, it is called nondipping BP. Conversely, reverse dipping BP means an increase in mean systolic BP instead of a drop during the night. Reverse dipping is observed in hypertension (HTN), diabetes mellitus (DM), chronic kidney disease (CKD), and obstructive sleep apnea (OSA) syndrome. The introduction of ambulatory BP monitoring (ABPM) led to the emergence of identifying normal and elevated BP patterns. Non-dipping BP increases the risk of cardiovascular system (CVS) complications such as left ventricular hypertrophy, proteinuria, glomerular filtration rate (GFR) reduction, and CKD progression. A loss or blunting of the normal BP profile is recognized as a deleterious variant, and restoring abnormal BP patterns has been reported to significantly impact end-organ damage, morbidity, and mortality. In this non-systematic clinically-oriented, comprehensive review, we aim to update the BP variables and the pathophysiology of nondipping BP and point out the areas which need more investigation from a nephrology perspective because the nondipping BP increases the risk of proteinuria, GFR reduction, and CKD progression. A literature search of PubMed, Google, EMBASE, and Google Scholar was conducted. Checks of selected papers and relevant reviews complemented the electronic search. With improved BP measurement methods, the physiology of BP profile variations is readily detectable during the day and night. A nondipping BP profile is a distinct BP pattern that may have significant end-organ damage effects and therapeutic importance for nephrologists. The pathophysiology of the nondipping BP variant must be clarified to prevent complications, and further investigations are required. Furthermore, there is debate about the best BP index to utilize: systolic BP, diastolic BP, mean arterial pressure, or a mixture of all. All these areas are important and need new research projects.

Pathophysiology of the Nondipping Blood Pressure Pattern

The nondipping blood pressure (BP) pattern corresponds to a disruption in the circadian BP rhythm with an insufficient decrease in BP levels during nighttime sleep as observed using 24-hour ambulatory BP monitoring. Patients with nondipping BP pattern have poorer renal and cardiovascular outcomes, independent of their average 24-hour BP levels. The pathophysiology of nondipping BP is complex and involves numerous mechanisms: perturbations of (1) the circadian rhythm, (2) the autonomic nervous system, and (3) water and sodium regulation. This review provides an outline of the pathways potentially involved in the nondipping BP profile in different conditions. A recent hypothesis is also discussed involving the role of gut microbiota in the dipping/nondipping patterns, via the fecal diet-derived short chain fatty acids.

Mid-Point of the Active Phase Is Better to Achieve the Natriuretic Effect of Acute Salt Load in Mice

Excess sodium intake and insufficient potassium intake are a prominent global issue because of their influence on high blood pressure. Supplementation of potassium induces kaliuresis and natriuresis, which partially explains its antihypertensive effect. Balancing of minerals takes place in the kidney and is controlled by the circadian clock; in fact, various renal functions exhibit circadian rhythms. In our previous research, higher intake of potassium at lunch time was negatively associated with blood pressure, suggesting the importance of timing for sodium and potassium intake. However, the effects of intake timing on urinary excretion remain unclear. In this study, we investigated the effect of 24 h urinary sodium and potassium excretion after acute sodium and potassium load with different timings in mice. Compared to other timings, the middle of the active phase resulted in higher urinary sodium and potassium excretion. In Clock mutant mice, in which the circadian clock is genetically disrupted, urinary excretion differences from intake timings were not observed. Restricted feeding during the inactive phase reversed the excretion timing difference, suggesting that a feeding-induced signal may cause this timing difference. Our results indicate that salt intake timing is important for urinary sodium and potassium excretion and provide new perspectives regarding hypertension prevention.

Controversies in Hypertension III: Dipping, Nocturnal Hypertension, and the Morning Surge

A comprehensive approach to hypertension requires out-of-office determinations by home and/or ambulatory monitoring. The 4 phenotypes comparing office and out-of-office pressures in treated and untreated patients include normotension, hypertension, white-coat phenomena, and masked phenomena. Components of out-of-office pressure may be equally as important as mean values. Nighttime pressures are normally 10 - 20% lower than daytime (normal "dipping"). Abnormalities include dipping more than 20% (extreme dippers), less than 10 % (non-dippers), or rising above daytime (risers) and have been associated with elevated cardiovascular risk. Nighttime pressure may be elevated (nocturnal hypertension) in isolation or together with daytime hypertension. Isolated nocturnal hypertension theoretically changes white-coat hypertension to true hypertension and normotension to masked hypertension. Pressure normally peaks in the morning hours ("morning surge") when cardiovascular events are most common. Morning hypertension may result from residual nocturnal hypertension or an exaggerated surge and has been associated with enhanced cardiovascular risk, especially in Asian populations. Randomized trials are needed to determine whether altering therapy based solely on either abnormal dipping, isolated nocturnal hypertension, and/or an abnormal surge is justified.

Higher Potassium Intake and Lower Sodium Intake May Help in Reducing CVD Risk by Lowering Salt Sensitivity of Blood Pressure in the Han Chinese Population

Sodium (Na) reduction with a parallel supplemental potassium (K) intake can prevent cardiovascular diseases (CVDs). The relationship of the urinary Na/K ratio and salt sensitivity of blood pressure (SSBP) with CVDs is not clearly explained. We assumed that the SSBP mediates the relationship between the Na/K ratio and CVDs. In total, 2055 subjects who had 24 h urine collected and SSBP determined were included in this study. CVD risk was estimated using the China-PAR equation. MediationMultivariate logistic regression was used to explore the associations between the Na/K ratio or SSBP with CVD risk. Mediation analysis using a logistic regression model was performed. Both the urinary Na/K ratio and SSBP were related to the estimated CVD risk (p < 0.05). The mediation analysis found that SSBP mediated approximately 12% of the association between Na/K ratio and CVD risk. Our findings indicate that higher K intake and lower Na intake may help in preventing CVD risk by reducing SSBP risk in individuals with normotension or stage-one hypertension.

Sex Differences in Diurnal Sodium Handling During Diet-Induced Obesity in Rats

BACKGROUND

Emerging evidence over the past several years suggests that diurnal control of sodium excretion is sex dependent and involves the renal endothelin system. Given recent awareness of disruptions of circadian function in obesity, we determined whether diet-induced obesity impairs renal handling of an acute salt load at different times of day and whether this varies by sex and is associated with renal endothelin dysfunction.

METHODS

Male and female Sprague-Dawley rats were placed on a high-fat diet for 8 weeks before assessing renal sodium handling and blood pressure.

RESULTS

Male, but not female, rats on high fat had a significantly reduced natriuretic response to acute NaCl injection at the beginning of their active period that was associated with lower endothelin 1 (ET-1) excretion, lower ET-1 mRNA expression in the cortex and outer medulla as well as lower ET_B receptor expression in the outer medulla of the high-fat rats. Obese males also had significantly higher blood pressure (telemetry) that was exacerbated by adding high salt to the diet during the last 2 weeks. While female rats developed hypertension with a high-fat diet, they were not salt sensitive and ET-1 excretion was unchanged.

CONCLUSIONS

These data identify diet-induced obesity as a sex-specific disruptive factor for maintaining proper sodium handling. Although high-fat diets induce hypertension in both sexes, these data reveal that males are at greater risk of salt-dependent hypertension and further suggest that females have more redundant systems that can be productive against salt-sensitive hypertension in at least some circumstances.

Abnormal Circadian Blood Pressure Variation is Associated with SYNTAX Scores in Hospitalized Patients with Acute Coronary Syndrome

BACKGROUND

Blunted nocturnal blood pressure (BP) reduction, referred to as non-dipper hypertension, is a strong predictor of cardiovascular morbidity and mortality.

OBJECTIVES

This study aimed to investigate the relationship between non-dipper hypertension and the severity and complexity of coronary artery disease using SYNTAX score in hospitalized patients with acute coronary syndrome.

METHODS

A total of 306 consecutive patients with acute coronary syndrome were screened. Patients who were clinically stable and admitted to the intermediate intensive care unit at least 24 hours after angiography and/or successful revascularization. After the exclusion criteria, 141 patients (34 female and 107 male; mean age 61 ± 11 years) were included. Non-dipper hypertension has been defined as a 0% to 10% decrease in average systolic BP at nighttime compared to daytime, measured at hourly intervals using the same automatic BP measuring device on bedside monitors (Vismo PVM-2701; Nihon Kohden Corp., Tokyo, Japan). SYNTAX score was calculated with an online calculator. The independent predictors of SYNTAX score were assessed using multivariable logistic regression analysis. P < 0.05 was considered statistically significant.

RESULTS

The patients with non-dipper hypertension had higher SYNTAX score than the patients with dipper hypertension (11.12 ± 6.41 versus 6.74 ± 6.45, p < 0.0001). In a multivariable logistic regression model, non-dipper hypertension status (odds ratio: 5.159; 95% confidence interval: 2.246 to 11.852, p < 0.001), sex (p = 0.012) and low-density lipoprotein cholesterol (p = 0.008) emerged as independent predictors of high SYNTAX score.

CONCLUSIONS

The results of our study provide a possible additional mechanism linking abnormal circadian BP profile with coronary artery disease severity and complexity in patients with acute coronary syndrome.

Impact of Percutaneous Transluminal Renal Angioplasty on Autonomic Nervous System and Natriuresis in Hypertensive Patients With Renal Artery Stenosis

Background

We investigated the early postoperative effect of percutaneous transluminal renal angioplasty on ambulatory blood pressure (BP) and the circadian characteristics of natriuresis and autonomic nerve activity.

Methods and Results

A total of 64 patients with hypertension with hemodynamically significant renal artery stenosis (mean age, 60.0±21.0 years; 31.3% fibromuscular dysplasia) who underwent angioplasty were included, and circadian characteristics of natriuresis as well as heart rate variability indices, including 24‐hour BP, low‐frequency and high‐frequency (HF) components, and the percentage of differences between adjacent normal R‐R intervals >50 ms were evaluated using an oscillometric device, TM‐2425, both at baseline and 3 days after angioplasty. In both the fibromuscular dysplasia and atherosclerotic stenosis groups, 24‐hour systolic BP (fibromuscular dysplasia, −19±14; atherosclerotic renal artery stenosis, −11±9 mm Hg), percentage of differences between adjacent normal R‐R intervals >50 ms, HF, brain natriuretic peptide, and nighttime urinary sodium excretion decreased (all P<0.01), and heart rate increased (both P<0.05) after angioplasty. In both groups, revascularization increased the night/day ratios of percentage of differences between adjacent normal R‐R intervals >50 ms (both P<0.01) and HF, and decreased those of low frequency/HF (all P<0.05) and nighttime urinary sodium excretion (fibromuscular dysplasia, 1.17±0.15 to 0.78±0.09; atherosclerotic renal artery stenosis, 1.37±0.10 to 0.99±0.06, both P<0.01). Multiple logistic regression analysis indicated that a 1‐SD increase in baseline low frequency/HF was associated with at least a 15% decrease in 24‐hour systolic BP after angioplasty (odds ratio, 2.30 [95% CI, 1.03–5.67]; P<0.05).

Conclusions

Successful revascularization results in a significant BP decrease in the early postoperative period. Intrarenal perfusion might be a key modulator of the circadian patterns of autonomic nerve activity and natriuresis, and pretreatment heart rate variability evaluation seems to be important for treatment success.

Short-term daytime restricted feeding in rats with high salt impairs diurnal variation of Na+ excretion

Night shift work increases risk of cardiovascular disease associated with an irregular eating schedule. Elevating this risk is the high level of salt intake observed in the typical Western diet. Renal Na⁺ excretion has a distinct diurnal pattern, independent of time of intake, yet the interactions between the time of intake and the amount of salt ingested are not clear. The hypothesis of the present study was that limiting food intake to the typically inactive period in addition to high-salt (HS) feeding will disrupt the diurnal rhythm of renal Na⁺ excretion. Male Sprague-Dawley rats were placed on either normal-salt (NS; 0.49% NaCl) or HS (4% NaCl) diets. Rats were housed in metabolic cages and allowed food ad libitum and then subjected to inactive period time-restricted feeding (iTRF) for 5 days. As expected, rats fed NS and allowed food ad libitum had a diurnal pattern of Na⁺ excretion. The diurnal pattern of Na⁺ excretion was not significantly different after 5 days of iTRF compared with ad libitum rats. In response to HS, the diurnal pattern of Na⁺ excretion was similar to NS-fed rats. However, this pattern was attenuated after 5 days of HS iTRF. The diurnal excretion pattern of urinary aldosterone was abolished in both NS iTRF and HS iTRF rats. These data support the hypothesis that HS intake combined with iTRF impairs circadian mechanisms associated with renal Na⁺ excretion.NEW & NOTEWORTHY Timing of food intake normally has little effect on the diurnal pattern of Na⁺ and water excretion. However, rats on a high-salt diet were unable to maintain this pattern, yet K⁺ excretion was more readily adjusted to match timing of intake. These data support the hypothesis that Na⁺ and water homeostasis are impacted by timing of high-salt diets.

Nocturnal Dipping and Left Ventricular Mass Index in the Chronic Kidney Disease in Children Cohort

BACKGROUND AND OBJECTIVES

The physiologic nocturnal BP decline is often blunted in patients with CKD; however, the consequences of BP nondipping in children are largely unknown. Our objective was to determine risk factors for nondipping and to investigate if nondipping is associated with higher left ventricular mass index in children with CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted a cross-sectional analysis of ambulatory BP monitoring and echocardiographic data in participants of the Chronic Kidney Disease in Children study. Multivariable linear and spline regression analyses were used to evaluate the relationship of risk factors with dipping and of dipping with left ventricular mass index.

RESULTS

Within 552 participants, mean age was 11 (±4) years, mean eGFR was 53 (±20) ml/min per 1.73 m2, and 41% were classified as nondippers. In participants with nonglomerular CKD, female sex and higher sodium intake were significantly associated with less systolic and diastolic dipping (P≤0.05). In those with glomerular CKD, Black race and greater proteinuria were significantly associated with less systolic and diastolic dipping (P≤0.05). Systolic dipping and diastolic dipping were not significantly associated with left ventricular mass index; however, in spline regression plots, diastolic dipping appeared to have a nonlinear relationship with left ventricular mass index. As compared with diastolic dipping of 20%-25%, dipping of <20% was associated with 1.41-g/m2.7-higher left ventricular mass index (95% confidence interval, -0.47 to 3.29), and dipping of >25% was associated with 1.98-g/m2.7-higher left ventricular mass index (95% confidence interval, -0.77 to 4.73), although these relationships did not achieve statistical significance.

CONCLUSIONS

Black race, female sex, and greater proteinuria and sodium intake were significantly associated with blunted dipping in children with CKD. We did not find a statistically significant association between dipping and left ventricular mass index.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2021_12_20_CJN09810721.mp3.

The stress, salt excretion, and nighttime blood pressure (SABRE) study: Rationale and study design

Background

Abnormal diurnal patterns of blood pressure (BP) on ambulatory BP monitoring (ABPM), defined by reduced BP dipping or elevated nighttime BP, are associated with increased risk for adverse cardiovascular events. Psychological stress is associated with abnormal diurnal patterns of BP. Exposure to an acute stressor (e.g., mental stress task) normally increases urinary sodium excretion. However, some individuals have sodium retention after stress provocation, revealing substantial between-person variability in the degree of stress-induced sodium excretion. Prior research suggests urinary sodium excretion that does not occur during the daytime may shift toward the nighttime, accompanied by an increase in nighttime BP. Associations between psychological stress and the diurnal patterns of sodium excretion and BP are not yet fully understood.

Design

The study is conducted in both the laboratory and naturalistic environment with a multi-racial/ethnic sample of 211 healthy adults. In the laboratory, change in urinary sodium excretion in response to mental stress tasks is examined with pre-/post-stress assessments of sodium excretion. Changes in angiotensin-II, catecholamines, BP, heart rate, endothelin-1, and cortisol are also assessed. In the 24-hour naturalistic environment, the diurnal patterns of sodium excretion and systolic BP are assessed as daytime-to-nighttime ratio of sodium excretion and ABPM, respectively. Ecological momentary assessments of perceived stress are also collected.

Summary

The SABRE study investigates previously unexplored associations between stress-induced urinary excretion in the laboratory, diurnal patterns of sodium excretion and BP in the naturalistic environment, and ecological stress. It has high potential to advance our understanding of the role of psychological stress in hypertension.

From salt to hypertension, what is missed?

Excess salt intake is viewed as a major contributor to hypertension and cardiovascular disease, and dietary salt restriction is broadly recommended by public health guidelines. However, individuals can have widely varying physiological responses to salt intake, and a tailored approach to evaluation and intervention may be needed. The traditional sodium related concepts are challenging to assess clinically for two reasons: (1) spot and 24-hour urine sodium are frequently used to evaluate salt intake, but are more suitable for population study, and (2) some adverse effects of salt may be blood pressure-independent. In recent years, previously unknown mechanisms of sodium absorption and storage have been discovered. This review will outline the limitations of current methods to assess sodium balance and discuss new potential evaluation methods and treatment targets.

Proteinuria and nocturnal blood pressure dipping in hypertensive children and adolescents

BACKGROUND

The absence of nocturnal blood pressure dipping is associated with adverse cardiovascular outcomes in adults, and proteinuria is a risk factor for non-dipping in this population. Risk factors for non-dipping in children are largely unknown.

METHODS

We retrospectively identified patients aged 5-19 years who underwent 24-h ambulatory blood pressure monitoring (ABPM) from August 2018 to January 2019 and had a spot urine protein-to-creatinine ratio (PCR) within 1 year of their ABPM. Dipping was defined as ≥10% reduction in systolic and diastolic blood pressure from day to night. Multivariable logistic and linear regression models evaluated the association of proteinuria with non-dipping.

RESULTS

Among 77 children identified, 27 (35.1%) were non-dippers. Each two-fold higher urine PCR was associated with 38% higher odds of non-dipping, after adjusting for body mass index (BMI). Higher urine PCR was also associated with a lower diastolic dipping percentage by 1.33 (95% confidence interval 0.31-2.34), after adjusting for BMI, age, and estimated glomerular filtration rate.

CONCLUSIONS

Limitations of this study include its retrospective design and the time lapse between urine PCR and ABPM. Proteinuria appears to be associated with blood pressure non-dipping in children. This finding needs to be confirmed in prospective studies.

IMPACT

Our study demonstrates the association of proteinuria with non-dipping of blood pressure in children. This association has been explored in adults, but to our knowledge, this is the first time it is evaluated in children referred for evaluation of elevated blood pressure. Non-dipping is a modifiable risk factor for kidney function decline and cardiovascular disease in adulthood, and thus early identification in children is important. The association between proteinuria and non-dipping in children will allow us to more readily identify those at risk, with a future focus on interventions to modify blood pressure dipping patterns.

Spot Urine Formulas to Estimate 24-Hour Urinary Sodium Excretion Alter the Dietary Sodium and Blood Pressure Relationship

[Figure: see text].

High prevalence of non-dipping patterns among Black Africans with uncontrolled hypertension: a secondary analysis of the CREOLE trial

BACKGROUND

Dipping of blood pressure (BP) at night is a normal physiological phenomenon. However, a non-dipping pattern is associated with hypertension mediated organ damage, secondary forms of hypertension and poorer long-term outcome. Identifying a non-dipping pattern may be useful in assessing risk, aiding the decision to investigate for secondary causes, initiating treatment, assisting decisions on choice and timing of antihypertensive therapy, and intensifying salt restriction.

OBJECTIVES

To estimate the prevalence and factors associated with non-dipping pattern and determine the effect of 6 months of three antihypertensive regimens on the dipping pattern among Black African hypertensive patients.

METHODS

This was a secondary analysis of the CREOLE Study which was a randomized, single blind, three-group trial conducted in 10 sites in 6 Sub-Saharan African countries. The participants were 721 Black African patients, aged between 30 and 79 years, with uncontrolled hypertension and a baseline 24-h ambulatory blood pressure monitoring (ABPM). Dipping was calculated from the average day and average night systolic blood pressure measures.

RESULTS

The prevalence of non-dipping pattern was 78% (564 of 721). Factors that were independently associated with non-dipping were: serum sodium > 140 mmol/l (OR = 1.72, 95% CI 1.17-2.51, p-value 0.005), a higher office systolic BP (OR = 1.03, 95% CI 1.01-1.05, p-value 0.003) and a lower office diastolic BP (OR = 0.97, 95% CI 0.95-0.99, p-value 0.03). Treatment allocation did not change dipping status at 6 months (McNemar's Chi2 0.71, p-value 0.40).

CONCLUSION

There was a high prevalence of non-dipping among Black Africans with uncontrolled hypertension. ABPM should be considered more routinely in Black Africans with uncontrolled hypertension, if resources permit, to help personalise therapy. Further research is needed to understand the mechanisms and causes of non-dipping pattern and if targeting night-time BP improves clinical outcomes. Trial registration ClinicalTrials.gov (NCT02742467).

The Correlation Between Urinary Sodium Excretion and Blood Pressure in Hospitalized Adult Patients with Hypertension

INTRODUCTION

This study was designed to understand the baseline salt intake of adult patients with hypertension in Shanxi Province, and to analyze the correlation between urinary sodium excretion and blood pressure.

METHODS

From June 2018 to December 2019, 16 hospitals with regional representativeness and experimental conditions in Shanxi Province were selected, and 643 eligible adult inpatients with primary hypertension were enrolled from these hospitals. The ages of patients ranged from 18 to 80 years. A 24-h ambulatory blood pressure monitoring was performed, and morning urine sodium concentration and 24-h urine sodium excretion were measured. The correlation between urinary sodium excretion and blood pressure in adult patients with hypertension was analyzed.

RESULTS

The baseline salt intake of the adult patient participants with hypertension in Shanxi Province was 11.51 g/day. The average 24-h urinary sodium excretion of all observed subjects was 191.90 ± 98.18 mmol. The 24-h urinary sodium excretion and morning urinary sodium concentration were significantly positively correlated with systolic and diastolic blood pressure following adjustment of confounding factors, including gender, age, body weight, and smoking.

CONCLUSION

The morning urine sodium concentration and 24-h urine sodium excretion were significantly positively correlated with blood pressure. High sodium excretion may be a risk factor for rhythm abnormalities in non-dipper pattern blood pressure. The control of urinary sodium concentration can thus be an important strategy for regulating abnormal blood pressure rhythm.

Defining the nocturnal period in 24-h ambulatory blood pressure monitoring: a comparison of three methods

OBJECTIVES

The purpose of our study was to compare three definitions of ambulatory blood pressure (BP) nocturnal period and to assess their agreement in determining nocturnal BP dipping patterns.

METHODS

We investigated 69 subjects with metabolic syndrome, aged 50-55 years. In all subjects, we assessed 24-h BP monitoring, electrocardiogram and actigraphy profiles. The nocturnal period was defined in three ways: as a fixed narrow nighttime period from 01:00 to 06:00, as a self-reported sleeping period and as a disappearance and onset of physical activity recorded by the actigraph.

RESULTS

Our study revealed a significant discrepancy between the self-reported and actigraphy-based nocturnal periods (P < 0.001). In addition, different definitions of the nighttime yielded significant differences in determining nondipping, extreme dipping and dipping BP patterns, the identification of the latter being affected the most. The actigraphy-based approach best aligned with the fixed-time determination of the nocturnal period: Cohen's kappa coefficient for the nondipping pattern was 0.78 (0.58-1), for the dipping pattern 0.75 (0.59-0.91) and for the extreme dipping pattern 0.81 (0.65-0.97). In comparison to the self-reported determination of the nocturnal period, using the actigraphy-based approach resulted in reclassifying the nocturnal BP pattern in 20.3% of subjects.

CONCLUSIONS

The lack of agreement between fixed-time, self-reported and actigraphy-based determinations of the nighttime period affects the identification of the nocturnal BP patterns. In comparison to the self-reported nocturnal period estimation, the actigraphy-based approach results in the reclassification of BP dipping status in every fifth subject.

HIV-positive demonstrate more salt sensitivity and nocturnal non-dipping blood pressure than HIV-negative individuals

Background

High dietary salt and a lack of reduced blood pressure (BP) at night (non-dipping) are risk factors for the development of hypertension which may result in end-organ damage and death. The effect of high dietary salt on BP in black people of sub-Saharan Africa living with HIV is not well established. The goal of this study was to explore the associations between salt sensitivity and nocturnal blood pressure dipping according to HIV and hypertension status in a cohort of adult Zambian population.

Methods

We conducted an interventional study among 43 HIV-positive and 42 HIV-negative adults matched for age and sex. Study participants were instructed to consume a low (4 g) dietary salt intake for a week followed by high (9 g) dietary salt intake for a week. Salt resistance and salt sensitivity were defined by a mean arterial pressure difference of ≤5 mmHg and ≥ 8 mmHg, respectively, between the last day of low and high dietary salt intervention. Nocturnal dipping was defined as a 10–15% decrease in night-time blood pressure measured with an ambulatory blood pressure monitor.

Results

The median age was 40 years for both the HIV-positive and the HIV-negative group with 1:1 male to female ratio. HIV positive individuals with hypertension exhibited a higher BP sensitivity to salt (95%) and non-dipping BP (86%) prevalence compared with the HIV negative hypertensive (71 and 67%), HIV positive (10 and 24%) and HIV-negative normotensive (29 and 52%) groups, respectively (p < 0.05). Salt sensitivity was associated with non-dipping BP and hypertension in both the HIV-positive and HIV-negative groups even after adjustment in multivariate logistic regression (< 0.001).

Conclusions

The results of the present study suggest that high dietary salt intake raises blood pressure and worsens nocturnal BP dipping to a greater extent in hypertensive than normotensive individuals and that hypertensive individuals have higher dietary salt intake than their normotensive counterparts. Regarding HIV status, BP of HIV-positive hypertensive patients may be more sensitive to salt intake and demonstrate more non-dipping pattern compared to HIV-negative hypertensive group. However, further studies with a larger sample size are required to validate this.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40885-020-00160-0.

Nondipping Blood Pressure: Predictive or Reactive Failure of Renal Sodium Handling?

Blood pressure follows a daily rhythm, dipping during nocturnal sleep in humans. Attenuation of this dip (nondipping) is associated with increased risk of cardiovascular disease. Renal control of sodium homeostasis is essential for long-term blood pressure control. Sodium reabsorption and excretion have rhythms that rely on predictive/circadian as well as reactive adaptations. We explore how these rhythms might contribute to blood pressure rhythm in health and disease.

The Healthy, Aging, and Diseased Kidney: Relationship with Cardiovascular Disease

The cardiovascular and renal systems share an intimate physiological relationship, wherein a perturbance in one system may have an adverse effect on the other. Since the burden of renal disease increases with age, there is a considerable interest in the pathophysiology of kidney disease in the geriatric patient population. This review will explore the physiological dynamics behind the increased susceptibility to kidney disease in this population. A better understanding of these pathophysiological changes may lead to improved prevention and management strategies.

Night-time systolic blood pressure and subclinical cerebrovascular disease: the Cardiovascular Abnormalities and Brain Lesions (CABL) study

AIMS

Although ambulatory blood pressure (BP) is a better predictor of cardiovascular outcomes than office BP, its association with subclinical cerebrovascular disease is not clarified. We investigated the associations of office and ambulatory BP values with subclinical cerebrovascular disease in a population based, predominantly elderly cohort without prior stroke.

METHODS AND RESULTS

Eight hundred and twenty-eight participants underwent 24-h ambulatory BP monitoring (ABPM), 2D echocardiography and brain magnetic resonance imaging in the Cardiac Abnormalities and Brain Lesion (CABL) study. Daytime, night-time, and 24-h BPs, nocturnal dipping pattern, morning surge (MS), and 24-h variability were assessed. Subclinical cerebrovascular disease was defined as silent brain infarcts (SBIs) and white matter hyperintensity volume (WMHV). The association of BP measures with the presence of SBI and upper quartile of log-WMHV (log-WMHV4) was analysed. SBIs were detected in 111 patients (13.4%). Mean log-WMHV was -0.99 ± 0.94. In multivariable analysis, only night-time systolic BP (SBP) was significantly associated with SBI [odds ratio (OR) 1.15 per 10 mmHg, P = 0.042], independent of cardiovascular risk factors, and pertinent echocardiographic parameters. Although daytime, night-time, 24-h BPs, and non-dipping pattern were all significantly associated with log-WMHV4 (all P < 0.05), night-time SBP showed the strongest association (OR 1.21 per 10 mmHg, P = 0.003) and was the sole independent predictor when tested against the other BP parameters. Office BP measures, MS, and BP variability were not associated with subclinical cerebrovascular disease in adjusted analyses.

CONCLUSION

Elevated night-time SBP is strongly associated with subclinical cerebrovascular disease. Night-time SBP by ABPM allows to identify individuals at higher risk of hypertensive brain injury.

Impaired Daytime Urinary Sodium Excretion Impacts Nighttime Blood Pressure and Nocturnal Dipping at Older Ages in the General Population

The circadian rhythm of urinary sodium excretion is related to the diurnal blood pressure regulation (BP) and the nocturnal dipping pattern. The renal sodium excretion expressed as daytime/nighttime ratio impacts BP, but a limited number of studies have investigated this topic to date. In this cross-sectional study, we aimed to investigate the impact of different daily patterns of sodium excretion (comparing low with high ratios) on BP and nocturnal dipping and to explore the relationship with age. Twenty-four-hour ambulatory BP monitoring and daytime and nighttime urinary sodium collections were used to assess 1062 subjects in Switzerland. Analyses were performed according to the day/night urinary sodium excretion ratio quartiles (Q1-Q4) and by age group (≤50 and ≥50 years). Subjects in Q1 can be considered low excretors of sodium during the daytime since the rate of sodium excretion during the daytime was 40% lower than that of subjects in Q4. Quartiles of the day/night urinary sodium excretion ratio showed that subjects in Q1 were 7 years older and had respectively 6 and 5 mmHg higher nighttime systolic and diastolic BP and a higher nocturnal dipping compared with subjects in Q4 (p-value ≤0.001). Associations found were significant only for subjects older than 50 years (all p < 0.05). The present results suggest that a decreased capacity to excrete sodium during daytime is more prevalent as age increases and that it impacts nighttime blood pressure and nocturnal dipping in older subjects.

Blood Pressure Increases Before Pulse Rate During the Nocturnal Period in Hypertensive Patients

Ambulatory blood pressure monitoring (ABPM) is used for the evaluation of out-of-office blood pressure (BP), however, knowledge concerning the detailed behavior of nocturnal blood pressure (BP) and pulse rate (PR) is limited.A total of 190 participants (64 ± 15 years, 46.3% males) underwent ABPM for diagnosis of hypertension or evaluation of hypertensive therapy. BP and PR were measured automatically by the oscillometric method. From the hourly average ABPM values, the nocturnal time courses (0 AM to 6 AM) of SBP and PR were determined and compared to each other.In general, SBP fell to the lowest level at around midnight and started to increase progressively towards dawn while PR stayed unchanged until 7 AM. Age and gender affected the time course of SBP, most distinctly in the female patients aged ≥ 60 years. The time course of the increase of SBP was very similar in the patients, with BP dipping and non-dipping. The cardiothoracic ratio (CTR) slightly and renal dysfunction modestly facilitated the increase of nocturnal SBP. The nocturnal increase in SBP was not accompanied by an increase of PR in any group or subgroup. The pathophysiology and clinical significance of the early and exclusive increase in nocturnal BP need to be investigated.Average ABPM values in these hypertensive patients showed that BP starts to increase toward dawn without an increase in PR and that this discrepant behavior between BP and RP was most distinct in females 60 or older. The mechanism and clinical significance of such a discordant variation in BP and PR need to be elucidated.

A Single Urine Sodium Measurement May Validly Estimate 24-hour Urine Sodium Excretion in Patients With an Ileostomy

BACKGROUND

Sodium deficiency in patients with an ileostomy is associated with chronic dehydration and may be difficult to detect. We aimed to investigate if the sodium concentration in a single spot urine sample may be used as a proxy for 24-hour urine sodium excretion.

METHODS

In a prospective observational study with 8 patients with an ileostomy and 8 volunteers with intact intestines, we investigated the correlations and agreements between spot urine sodium concentrations and 24-hour urine sodium excretions. Spot urine samples were drawn from every micturition during 24 hours, and relevant blood samples were drawn. All participants documented their food and fluid intakes.

RESULTS

There was a high and statistically significant correlation between 24-hour natriuresis and urine sodium concentrations in both morning spot samples (n = 8, Spearman's rho [ρ] = 0.78, P = 0.03) and midday spot samples (n = 8, ρ = 0.82, P = 0.02) in the patients with an ileostomy. The agreement between methods was fair (bias = -1.5, limits of agreement = -32.3 to 29.4). There were no statistically significant associations for evening samples or for samples from volunteers with intact intestines independently of time of day.

CONCLUSION

A single spot urine sodium sample obtained in the morning or midday may estimate 24-hour urine sodium excretion in patients with an ileostomy and thus help to identify sodium depletion.

Comparison of Urinary Sodium and Blood Pressure Relationship From the Spot Versus 24-Hour Urine Samples

Background We compared the relationship between sodium (Na) intake and blood pressure when Na intake was estimated from first- and second-morning spot urine samples using the INTERSALT (International Study on Salt and Blood Pressure) formula, versus directly measured 24-hour samples. Methods and Results We collected 24-hour urine and first- and second-morning voids of 383 participants in coastal Bangladesh for 2 visits. We measured participants' blood pressure using an Omron® HEM-907 monitor. To assess the shape of the relationship between urinary Na and blood pressure, we created restricted cubic spline plots adjusted for age, sex, body mass index, smoking and alcohol consumption, physical activities, religion, sleep hours, and household wealth. To assess multicollinearity, we reported variance inflation factors, tolerances, and Leamer's and Klein's statistics following linear regression models. The mean daily urinary Na was 122 (SD 26) mmol/d for the first; 122 (SD 27) mmol/d for the second; and 134 (SD 70) mmol/d for the 24-hour samples. The restricted cubic spline plots illustrated no association between first-morning urinary Na and systolic blood pressure until the 90th percentile distribution followed by a downward relationship; a nonlinear inverse-V-shaped relationship between second-morning urinary Na and systolic blood pressure; and a monotonic upward relationship between 24-hour urinary Na and systolic blood pressure. We found no evidence of multicollinearity for the 24-hour urinary Na model. Conclusions The urinary Na and systolic blood pressure relationship varied for 3 urinary Na measurements. Twenty-four-hour urinary Na captured more variability of Na intake compared with spot urine samples, and its regression models were not affected by multicollinearity.

Moving the Needle on Hypertension: What Knowledge Is Needed?

This review highlights the gaps in knowledge and methodological challenges discussed during the Experimental Biology 2019 expert panel session titled "Moving the Needle on Hypertension: What Knowledge Is Needed?" Hypertension is a critical public health burden. Despite a demonstrated benefit of blood pressure reduction on measures of hypertension-related morbidity and mortality, rates for successful blood pressure control remain low. Dietary sodium reduction has been shown to reduce both systolic blood pressure by approximately 3.2 mm Hg and diastolic blood pressure by 2.3 mm Hg, depending on baseline blood pressure and degree of sodium reduction. The updated Dietary Reference Intakes for adults released by the National Academies of Sciences, Engineering, and Medicine include a Chronic Disease Risk Reduction sodium intake level of 2300 mg/d, highlighting the importance of dietary sodium intake in reducing elevated blood pressure and indicating that reducing intakes to this level is expected to reduce blood pressure and risk of cardiovascular disease. The average US daily sodium intake of 3400 mg/d is well above the Chronic Disease Risk Reduction of 2300 mg/d, suggesting that dietary sodium reduction has the potential to significantly improve public health. Although the National Academies of Sciences, Engineering, and Medicine report presents intake recommendations based on a systematic, comprehensive, and thorough evaluation of the evidence, several challenges to moving the needle on hypertension remain. Success will require a more advanced understanding of sodium and potassium physiology, as well as development of the tools needed to effectively address existing research gaps and reduce barriers to sodium intake reduction.

Expert panel consensus recommendations for ambulatory blood pressure monitoring in Asia: The HOPE Asia Network

Hypertension is an important public health issue because of its association with a number of significant diseases and adverse outcomes. However, there are important ethnic differences in the pathogenesis and cardio-/cerebrovascular consequences of hypertension. Given the large populations and rapidly aging demographic in Asian regions, optimal strategies to diagnose and manage hypertension are of high importance. Ambulatory blood pressure monitoring (ABPM) is an important out-of-office blood pressure (BP) measurement tool that should play a central role in hypertension detection and management. The use of ABPM is particularly important in Asia due to the specific features of hypertension in Asian patients, including a high prevalence of masked hypertension, disrupted BP variability with marked morning BP surge, and nocturnal hypertension. This HOPE Asia Network document summarizes region-specific literature on the relationship between ABPM parameters and cardiovascular risk and target organ damage, providing a rationale for consensus-based recommendations on the use of ABPM in Asia. The aim of these recommendations is to guide and improve clinical practice to facilitate optimal BP monitoring with the goal of optimizing patient management and expediting the efficient allocation of treatment and health care resources. This should contribute to the HOPE Asia Network mission of improving the management of hypertension and organ protection toward achieving "zero" cardiovascular events in Asia.

The renal molecular clock: broken by aging and restored by exercise

The mammalian circadian clock governs physiological, endocrine, and metabolic responses coordinated in a 24-h rhythmic pattern by the suprachiasmatic nucleus (SCN) of the anterior hypothalamus. The SCN also dictates circadian rhythms in peripheral tissues like the kidney. The kidney has several important physiological functions, including removing waste and filtering the blood and regulating fluid volume, blood osmolarity, blood pressure, and Ca²⁺ metabolism, all of which are under tight control of the molecular/circadian clock. Normal aging has a profound influence on renal function, central and peripheral circadian rhythms, and the sleep-wake cycle. Disrupted circadian rhythms in the kidney as a result of increased age likely contribute to adverse health outcomes such as nocturia, hypertension, and increased risk for stroke, cardiovascular disease, and end organ failure. Regular physical activity improves circadian misalignment in both young and old mammals, although the precise mechanisms for this protection remain poorly described. Recent advances in the heart and skeletal muscle literature suggest that regular endurance exercise entrains peripheral clocks, and we propose that similar beneficial adaptations occur in the kidney through regulation of renal blood flow and fluid balance.

Osmotic indices and kidney concentrating activity: population-based data on correlates and prognostic power

Background

Research data are limited on indices of osmotic equilibrium and of kidney concentrating activity (KCA). This study investigated correlates and prognostic power of these indices in a sample of the general population.

Methods

Urine osmolality (U-osm), plasma osmolality (P-osm), plasma creatinine and other variables were measured by the Gubbio Study for the 1988-92 exam (baseline). Plasma creatinine and other variables were re-measured in the 2001-07 exam (follow-up). KCA was assessed as the U-osm/P-osm ratio and kidney function as estimated glomerular filtration rate (eGFR).

Results

Baseline data were complete in 4220 adults, of whom 852 died before follow-up and 2795 participated in the follow-up. At baseline, the following independent cross-sectional associations were identified: female sex and higher urine flow with lower values of U-osm, P-osm and U-osm/P-osm ratio (P < 0.01); obesity with higher values of U-osm, P-osm and U-osm/P-osm ratio (P < 0.01); older age and lower eGFR with lower U-osm, lower U-osm/P-osm ratio and higher P-osm (P < 0.05); hypertension and smoking with lower U-osm and lower U-osm/P-osm ratio (P < 0.05) but not with P-osm. From baseline to follow-up, the annualized rate was 1.26% for mortality and -0.74 ± 0.76 mL/min × 1.73 m2 for eGFR change. Mortality was independently predicted by baseline U-osm and baseline U-osm/P-osm ratio (hazard ratio for one higher standard deviation was ≤0.91, 95% confidence interval was ≤0.97, P < 0.01), but not by baseline P-osm. The eGFR change was not independently predicted by baseline values of U-osm, P-osm and U-osm/P-osm ratio (P ≥ 0.4).

Conclusions

Sex, age, obesity, eGFR, urine flow, hypertension and smoking independently associated with U-osm and KCA. U-osm and KCA independently predicted mortality, but not kidney function change over time.

Race and sex differences in asleep blood pressure: The Coronary Artery Risk Development in Young Adults (CARDIA) study

Nocturnal hypertension and non-dipping blood pressure are each associated with increased risk of cardiovascular disease. We determined differences in nocturnal hypertension and non-dipping systolic/diastolic blood pressure among black and white men and women who underwent 24-hour ambulatory blood pressure monitoring at the Coronary Artery Risk Development in Young Adults study Year 30 Exam in 2015-2016. Asleep and awake periods were determined from actigraphy complemented by sleep diaries. Nocturnal hypertension was defined as mean asleep systolic/diastolic blood pressure ≥ 120/70 mm Hg. Non-dipping systolic and diastolic blood pressure, separately, were defined as a decline in awake-to-asleep blood pressure < 10%. Among 767 participants, the prevalence of nocturnal hypertension was 18.4% and 44.4% in white and black women, respectively, and 36.4% and 59.9% in white and black men, respectively. After multivariable adjustment and compared with white women, the prevalence ratio (95% confidence interval) for nocturnal hypertension was 1.65 (1.18-2.32) for black women, 1.63 (1.14-2.33) for white men, and 2.01 (1.43-2.82) for black men. The prevalence of non-dipping systolic blood pressure was 21.5% and 41.0% in white and black women, respectively, and 20.2% and 37.9% in white and black men, respectively. Compared with white women, the multivariable-adjusted prevalence ratio (95% confidence interval) for non-dipping systolic blood pressure was 1.66 (1.18-2.32), 0.91 (0.58-1.42) and 1.66 (1.15-2.39) among black women, white men, and black men, respectively. Non-dipping diastolic blood pressure did not differ by race-sex groups following multivariable adjustment. In conclusion, black women and men have a high prevalence of nocturnal hypertension and non-dipping systolic blood pressure.

Sleep biology updates: Hemodynamic and autonomic control in sleep disorders

Sleep disorders like obstructive sleep apnea syndrome, periodic limb movements in sleep syndrome, insomnia and narcolepsy-cataplexy are all associated with an increased risk of cardiovascular diseases. These disorders share an impaired autonomic nervous system regulation that leads to increased cardiovascular sympathetic tone. This increased cardiovascular sympathetic tone is, in turn, likely to play a major role in the increased risk of cardiovascular disease. Different stimuli, such as intermittent hypoxia, sleep fragmentation, decrease in sleep duration, increased respiratory effort, and transient hypercapnia may all initiate the pathophysiological cascade leading to sympathetic overactivity and some or all of these are encountered in these different sleep disorders. In this manuscript, we outline the different pathways leading to sympathetic over-activity in different sleep conditions. This augmented sympathetic tone is likely to play an important role in the development of cardiovascular disease in patients with sleep disorders, and it is further hypothesized to that sympathoexcitation contributes to the metabolic dysregulation associated with these sleep disorders.

Impact of Ambulatory Blood Pressure on Early Cardiac and Renal Dysfunction in Hypertensive Patients without Clinically Apparent Target Organ Damage

PURPOSE

Impaired left ventricular (LV) global longitudinal strain (GLS) and the presence of microalbuminuria indicate early cardiac and renal dysfunction. We aimed to determine the relationships among 24-h ambulatory blood pressure (BP) variables, LV GLS, and urine albumin creatinine ratio (UACR) in hypertensive patients.

MATERIALS AND METHODS

A total of 130 hypertensive patients (mean age 53 years; 59 men) underwent 24-h ambulatory BP monitoring, measurements of peripheral and central BPs, and transthoracic echocardiography. Patients with apparent LV systolic dysfunction (LV ejection fraction <50%) or chronic kidney disease were not included. LV GLS was calculated using two-dimensional speckle tracking, and UACR was analyzed from spot urine samples.

RESULTS

In simple correlation analysis, LV GLS showed the most significant correlation with mean daytime diastolic BP (DBP) (r=0.427, p<0.001) among the various BP variables analyzed. UACR revealed a significant correlation only with night-time mean systolic BP (SBP) (r=0.253, p=0.019). In multiple regression analysis, daytime mean DBP and night-time mean SBP were independent determinants for LV GLS (β=0.35, p=0.028) and log UACR (β=0.49, p=0.007), respectively, after controlling for confounding factors. Daytime mean DBP showed better diagnostic performance for impaired LV GLS than did peripheral or central DBPs, which were not diagnostic. Night-time mean SBP showed satisfactory diagnostic performance for microalbuminuria.

CONCLUSION

There are different associations for daytime and night-time BP with early cardiac and renal dysfunction. Ambulatory BP monitoring provides more relevant BP parameters than do peripheral or central BPs regarding early cardiac and renal dysfunction in hypertensive patients.

The association of nocturnal hypertension and nondipping blood pressure with treatment-resistant hypertension: The Jackson Heart Study

Apparent treatment-resistant hypertension (aTRH), nocturnal hypertension, and nondipping blood pressure (BP) have shared risk factors. The authors studied the association between aTRH and nocturnal hypertension and aTRH and nondipping BP among 524 black Jackson Heart Study participants treated for hypertension. Nocturnal hypertension was defined by mean nighttime systolic BP ≥120 mm Hg or diastolic BP ≥70 mm Hg. Nondipping BP was defined by mean nighttime to daytime systolic BP ratio >0.90. aTRH was defined by mean clinic systolic BP ≥140 mm Hg and/or diastolic BP ≥90 mm Hg with three medication classes or treatment with four or more classes. The risk for developing aTRH associated with nondipping BP and nocturnal hypertension was estimated. After multivariable adjustment, participants with aTRH were more likely to have nocturnal hypertension (prevalence ratio, 1.20; 95% confidence interval, 1.03-1.39) and nondipping (prevalence ratio, 1.25; 95% confidence interval, 1.09-1.43). Over a median 7.3 years of follow-up, nocturnal hypertension and nondipping BP at baseline were not associated with developing aTRH after adjustment.

Renal Na-handling defect associated with PER1-dependent nondipping hypertension in male mice

Many physiological functions have a circadian rhythm, including blood pressure (BP). BP is highest during the active phase, whereas during the rest period, BP dips 10-20%. Patients that do not experience this dip at night are termed "nondippers." Nondipping hypertension is associated with increased risk of cardiovascular disease. The mechanisms underlying nondipping hypertension are not understood. Without the circadian clock gene Per1, C57BL/6J mice develop nondipping hypertension on a high-salt diet plus mineralocorticoid treatment (HS/DOCP). Our laboratory has shown that PER1 regulates expression of several genes related to sodium (Na) transport in the kidney, including epithelial Na channel (ENaC) and Na chloride cotransporter (NCC). Urinary Na excretion also demonstrates a circadian pattern with a peak during active periods. We hypothesized that PER1 contributes to circadian regulation of BP via a renal Na-handling-dependent mechanism. Na-handling genes from the distal nephron were inappropriately regulated in KO mice on HS/DOCP. Additionally, the night/day ratio of Na urinary excretion by Per1 KO mice is decreased compared with WT (4 × vs. 7×, P < 0.001, n = 6 per group). Distal nephron-specific Per1 KO mice also show an inappropriate increase in expression of Na transporter genes αENaC and NCC. These results support the hypothesis that PER1 mediates control of circadian BP rhythms via the regulation of distal nephron Na transport genes. These findings have implications for the understanding of the etiology of nondipping hypertension and the subsequent development of novel therapies for this dangerous pathophysiological condition.

Physician perceptions of blood pressure control in patients with chronic kidney disease and target blood pressure achievement rate

Background

Blood pressure (BP) control is the most-established method for the prevention of chronic kidney disease (CKD) progression. However, the ideal BP target for CKD patients is still under debate.

Methods

We performed a survey of regular registered members of the Korean Society of Nephrology to determine physician perceptions of BP control in patients with CKD. In addition, we evaluated the target BP achievement rate using data from the APrODiTe-2 study.

Results

Two-thirds of physicians considered the target BP for CKD to be < 130/85 mmHg. The systolic BP (SBP) thresholds for diabetic CKD, proteinuria ≥ 300 mg/day, 30 ≤ glomerular filtration rate (GFR) < 60 mL/min/1.73 m², age < 60 years, and the presence of atherosclerotic (ASO) complications were significantly lower than the SBP thresholds of the opposite parameters. The three major hurdles to controlling BP were non-compliance with lifestyle modification and medications, and self-report of well-controlled home BP. Most physicians prescribed home and ambulatory BP monitoring to less than 50% of their patients. The target BP achievement rates using the SBP thresholds in this survey were as follows: non-diabetic (69.3%); diabetic (29.5%); proteinuria < 300 mg/day (72.3%); proteinuria > 300 mg/day (33.7%); GFR ≥ 60 (76.4%); GFR < 30 (47.8%); no evidence of ASO (67.8%); and the presence of ASO (42.9%).

Conclusion

The target BP was lower in patients with higher cerebro-cardiovascular risks. These patient groups also showed lower target BP achievement rates. We also found a relatively lower application and clinical reflection rate of home or ambulatory BP monitoring.

Plasma microRNA-155-5p is increased among patients with chronic kidney disease and nocturnal hypertension

MicroRNAs play multiple roles in the regulation of blood pressure (BP). Nevertheless, to date, no study has assessed the association between microRNA plasma expression and BP control in chronic kidney disease (CKD) patients. Given this background, we evaluated the plasma expression of miR-155-5p, a translational inhibitor of angiotensin receptor type I, in CKD patients, to determine the association between miR-155-5p level and BP control. In this single-center cross-sectional study, we analyzed the miR-155-5p concentration by quantitative reverse transcriptase polymerase chain reaction using the U6 snRNA as a reference gene and 24-hour ambulatory blood pressure monitoring in CKD patients (stage ≥2) in relation to a control group of healthy age-matched and gender-matched individuals, with normal BP proven by the ambulatory blood pressure monitoring. We enrolled a total of 105 patients with CKD (stages 2-5, including 33 kidney renal transplant recipients), aged 59 ± 14 years; 47% males and 26 healthy volunteers (aged 55 ± 13, 50% male). Within the study group, a total of 36 patients (40%) presented with an average 24-hour systolic BP (SBP) ≥130 mm Hg and 41 patients (45%) presented nocturnal hypertension (NHT; SBP ≥120 mm Hg or diastolic BP ≥ 70 mm Hg). miRNA-155-5p was increased in plasma of CKD patients with median expression relative to control subjects equal to 2.92 (1.34-5.58). Interestingly, the plasma miRNA-155-5p expression was significantly higher in patients with NHT: 4.04 (2.92-10.8) versus 2.01 (1.21-3.07), P = .001 and its expression maintained an independent association with the average nocturnal SBP (coefficient B = 4.368, P = .047) by a multivariate regression analysis adjusted for confounders. The miR-155-5p was increased among CKD patients and further increased among subjects presenting with NHT. Further studies are warranted to determine the role of this non-coding RNA as a potential novel biomarker and therapeutic target in the non-dipping CKD individuals, characterized by increased cardiovascular risk.

Associations of Nocturnal Blood Pressure With Cognition by Self-Identified Race in Middle-Aged and Older Adults: The GENOA (Genetic Epidemiology Network of Arteriopathy) Study

BACKGROUND

Whether the association of blood pressure (BP) during sleep (nocturnal BP) with cognition differs by race is unknown.

METHODS AND RESULTS

Participants in the GENOA (Genetic Epidemiology Network of Arteriopathy) Study underwent ambulatory BP measurements, brain magnetic resonance imaging, and cognitive function testing (the Rey Auditory Verbal Learning Test, the Digit Symbol Substitution Task, and the Trail Making Test Part B) between 2000 and 2007. We examined multivariable linear regression models of the nocturnal BP-cognition association. Among 755 participants (mean age, 63 years; 64% women; 42% self-identified black race; 76% taking antihypertensive medication), mean nocturnal systolic BP (SBP)/diastolic BP was 126/69 mm Hg, daytime SBP/diastolic BP level was 139/82 mm Hg, and mean reduction in SBP from day to night (dipping) was 9%. Among the entire sample, a race interaction was observed in Digit Symbol Substitution Task and Trail Making Test Part B (both P<0.15). Race-stratified analyses showed that a 1-SD increase in nocturnal SBP levels was associated with poorer Digit Symbol Substitution Task and log-transformed Trail Making Test Part B scores (unstandardized regression coefficient [95% confidence interval]: -1.98 [-3.28 to -0.69] and 0.06 [0.004-0.12]; both P<0.05) in black but not white individuals. Additional adjustments for white matter hyperintensity volumes or brain atrophy, measured via brain magnetic resonance imaging, did not change the results. Results were similar when nocturnal SBP dipping was assessed as the exposure, yet daytime SBP levels yielded no association with cognition.

CONCLUSIONS

Nocturnal SBP measurements may be useful in assessing the potential risk for lower cognitive function in middle-aged and older adults, particularly in black individuals.

Comparison of Prognostic Values of Daytime and Night-Time Systolic Blood Pressures on Renal Outcomes in Patients With Chronic Kidney Disease

BACKGROUND

Differences in the predictive value of daytime systolic blood pressure (SBP) and night-time SBP by ambulatory blood pressure monitoring on renal outcomes have not been fully investigated in chronic kidney disease (CKD) patients. This study compared the prognostic value between daytime and night-time SBP on renal outcomes in CKD.Methods and Results:This prospective observational study included 421 patients. The composite renal endpoint was endstage renal disease (ESRD) or death. Cox models were used to determine associations of daytime and night-time SBP with renal outcomes. There were 150 renal events (ESRD, 130; death, 20). Multivariable Cox analyses demonstrated that hazard ratios (HRs) [95% confidence interval (CI)] for composite renal outcomes of every 10-mmHg increase in daytime and night-time SBP levels were 1.13 (1.02-1.26) (P=0.02) and 1.15 (1.05-1.27) (P<0.01), respectively. In addition, compared with the 1st daytime or night-time SBP quartile, HRs (95% CI) for outcomes in the 2nd, 3rd, and 4th quartiles were: daytime SBP, 1.25 (0.70-2.25), 1.09 (0.61-1.94), and 1.58 (0.88-2.85; P=0.13) (P for trend=0.16); night-time SBP, 1.09 (0.61-1.96), 1.31 (0.76-2.28), and 1.82 (1.00-3.30; P=0.049) (P for trend=0.03), respectively.

CONCLUSIONS

Night-time SBP appeared superior to daytime SBP for predicting renal outcomes in this population of patients.